Production of wood preservatives from coal tar fractions



July 28, l942 J. E. HARVEY, JR 2,291,303

PRODUCTION4 OF WOOD PRESERVATIVES FROM COAL TAR FRACTONS Fil ed Aug. 14, 1940 Patented July 28, 1942 UNITED STATES PRODUCTION F WOOD PRESERVATIVES FROM COAL TAR FRACTIONS Jacquelin E. Harvey, Jr., Atlanta, Ga., assignor of one-half to Southern Wood Preserving Colnpany, East Point, Ga., a. corporation of Georgia Application August 14, 1940, Serial No. 352,664

2 Claims. (Cl. 196-53) The present invention relates to the production of wood preservatives of enhanced value from tars of aromatic content and fractions thereof including pitches and high boiling fractions thereof, characterized by content of oxygenated compounds and sulphur.

An object of the present invention is the induction of toxicity in hydrocarbons having little or no toxicity, and of increasing toxicity in hydrocarbons having toxicity, whereby to provide, among other things, wood preserving oils of lowered corrosivity and induced toxicity, or, materials having induced toxicity and lowered corrosivity adapted to be added to wood preserving oils or the like.

Another object of the present invention is the improving of toxic value in wood preserving oils of current manufacture; the improving of toxic properties in the parent materials of wood preserving distillate of current manufacture; and the improving of toxic properties in residual material resulting from a distillation recovery of wood preserving oils or the like; the improving of toxic properties being preceded by lowering of corrosivity, and the process of toxicity induction being enhanced by the inclusion of catalytic means adapted to influence the decomposition of oxygenated compounds contained in the starting material, while under action of hydrogen.

Other objects of the present invention will be apparent from the following disclosures.

The invention will be understood from the following description of illustrative steps comprising various methods of securing the objects of the invention, when read in connection with the accompanying drawing wherein the figure is a diagrammatic sketch of an apparatus for carrying out a form of the process of the invention and wherein the nature of the step carried out in each chamber and the contents thereof are indicated by legend.

Example 1.-A sulfur bearing coal tar creosote of known toxic value, characterized by content of oxygenated compoundsspecic gravity of substantially 1.08, a coke residue in the order of 2% and substantially 35% residue above 355 C. is treated with hydrogen at a temperature of 350 C. and a pressure of 200 atmospheres; the thus treated creosote will be found upon inspection to have reduced corrosivity which advantage will pass to the finally processed material. The coal tar creosote of reduced sulfur content is passed through a high pressure chamber while simultaneously flowing hydrogen therewith, at a-temperature of 400 C. and pressure of 200 atmospheres. The catalyst is molybdenum oxide and tin chloride, flow of hydrogen 11,000 cubic feet per barrel creosote, and the time of reaction 45 minutes. The beneflciated creosote owing from the reactor is inspected and will be found to have an increased toxic property as stemming from among other things reduced coke residue, specic gravity, and viscosity. It will be found that there has been induced no substantial percentage of liquid chain structures or other liquids of relatively low toxicity that precluded the induction of toxicity.

By the effect of the presence of the tin chloride catalyst, the decomposition of oxygenated compound is influenced while under the action of hydrogen, thereby enhancing toxicity induction.

In the event any unwanted percentage of low boiling fractions exist after treatment, they may be stripped to make the newly formed oil of induced toxicity and lowered corrosivity conform in its low boiling end to a wood preservative of trade acceptance.

Example 2.-A sulfur bearing coal tar, specific gravity 1.1641 and characterized by a coke residue in excess of 8% and oxygenated compound is treated with hydrogen at a temperature of 375 C. and a pressure of 200 atmospheres; the thus treated coal tar will be found upon inspection to have reduced corrosivity which advantage will be reflected in the finally processed material. The coal tar of reduced sulfur content is passed through a high pressure reaction chamber while simultaneously flowing hydrogen therewith at a temperature of 395 C, and a pressure of 300 atmospheres while contacting vanadium oxide and iodoform catalytic materials. The flow of hydrogen is 12,000 cubic feet per barrel feed stock and the time of reaction is one hour.

The term Jcoal tar as used herein means tar produced by the high temperature carbonization of coal, as for instance, high temperature coke oven tar and gas house tar.

Eample 3.--A sulfur bearing coal tar fraction whose initial boiling point is substantially 240 C. and characterized by content of high molecular complexes and oxygenated compounds is treated with hydrogen at a pressure of 200 atmospheres and a temperature of 380 C.; the thus treated coal tar fraction will be found upon inspection to have reduced corrosivity which reduction will pass to the finally processed material. The coal tar fraction of reduced sulfur content is subjected to the action of a ow of hydrogen in the presence of molybdenum oxide and ammonium chloride catalytic materials while passing said tar fractions through a high pressure reaction chamber at a temperature of 400 C. and a pressure of 400 atmospheres. The flow of hydrogen is 15,000 cubic feet per barrel feed stock and the reaction period minutes.

The beneficiated coal tar fraction flowing from the reactor is inspected and found to have increased toxic value as stemming from among other things reduced coke residue, specific gravity, and viscosity, and the fact that no substantial percentage of liquid chain structures or other liquids of relatively low toxicity had been induced to lower toxicity, or, to make the induced toxicity of the present invention impossible.

In the event any percentage of undesirable low boiling fractions exist in the beneciated tar, said undesirable low boiling fractions may be stripped to provide conformance in the low boiling ends to a wood preservative of trade acceptance. Thus, by the process of the present invention there is provided a wood preserving oil of induced toxicity and lowered corrosivity that conforms in its low boiling end to a wood preservative of trade acceptance, said toxicity induction being enhanced by the effect of the presence of the catalytic material adapted to influence the decomposition of oxygenated compounds contained in thestarting materials.

If desired the beneciated tar or fractions thereof may be distilled for the recovery of a wood preserving distillate of enhanced toxic value; the distillation recovery may be effected to an upper limit so that the distillate will conform in its lower boiling end to a wood preserving oil of trade acceptance; or, the distillation may be effected to any desired upper limit with the removal of, if necessary, low boiling fractions in said distillate to provide specification performance.

In accordance with the process with the present invention, wood preserving oil of varying distillation characteristics may be provided, as for instance, providing substitutes for any of the wood preserving oils noted in the following:

Woon PREsERvINc IMPREGNANTS Specification 1. A. W. P. A.:

a. Up to 210 C., not more than 5% b. Up to 235 C., not more than 25% 2. A. W. P. A.:

a. Up to 210 C., not more than 1% b. Up to 235 C., not more than 10% c. Up to 355 C., not less than 65% 3. A. W. P. A.:

a. Up to 235 C., not more than 11/2% b. Up to 300 C., not more than ll/2% c. Up to 355 C., not less than 45% 4. A. W. P. A.:

a. Up to 210 C., not more than 8% b. Up to 235 C., not more than 35% 5. A. W. P. A.:

a. Up to 210 C., not more than 10% b. Up to 235 C., not more than 40% 6. A. W. P. A.:

a. Up to 210 C., not more than 5% b. Up to 235 C., not more than 15% 7. Prussian Ry.:

a. Up to 150 C., not more than 3% b. Up to 200 C., not more than 10% c. Up to 235 C., not more than 25% 8. N. P. V. & L. A. #220:

a. 5% at 162 C. b. 97% at 257 C. 9. S. P. S. S. O.:

a. 5% at 137 C. b. 95% at 257 C. 10. N. S. S. O.:

a. I. B. P., 150 C. b. 5% at 205 C. c. 95% at 292 C.

The abbreviations used in the foregoing are explained as follows: A. W. P. A., American Wood Preservers Association; N. P. V. & L. A., National Paint, Varnish & Lacquer Association S. P. S. S. O., Southern Pine 'Shingle Stain Oil; N. S. S. O., Neville Shingle Stain Oil.

Catalyst of the present invention are oxides, as for instance oxides of the sixth and eighth periodic groups; the oxides of other groups are usable, however, diiiicultly reducible oxides are preferred.

Reaction conditions in the step that lowers corrosivity by the action of hydrogen may be chosen from a wide range of temperatures and pressures inasmuch as sulfur reduction occurs at lowered temperatures and pressures. The lower limit of temperature and pressure is advisably that temperature and pressure which effects said reduction in a commercial manner, as regards the time element; pressures as high as practicable may be used, and the permissible upper limit of temperature is that temperature which causes under the conditions of the process no substantial deposition of carbon, as for instance a @cking action.

The step characterized by reduction of corrosivity may be carried on in a high pressure bomb or in a continuous manner in a reaction chamber or several reaction chambers, and in the event of continuous practice, the hydrogen liow is preferably maintained so as to induce no substantial carbon deposit, as for instance cokng. In the second cycle of hydrogen action, flows of hydrogen in the order of 8,000-15,000 cubic feet per barrel feed have proven satisfactory; however, higher or lower flows may be used, the high and low limits thereof being defined as those ows that induce no undesirable coking.

By the term benefciated as used herein and in the appended claims is meant the starting material at least once subjected to the action of hydrogen in accordance with the present process.

Starting materials consist of tars of aromatic content and fractions thereof characterized by sulfur content and content of oxygenated compounds, capable of having toxicity induced therein and may have been previously subjected to the action of hydrogen.

The present invention is predicated on, among other things, controlling action of hydrogen in both cycles so that no substantial percentage of liquid chain structures or other liquids of relatively low toxicity are induced that would preclude aforesaid toxicity induction. Hydrogen action is also controlled so that no substantial percentage of the starting material is converted to coke or carbon deposits.

The second cycle of hydrogen action may be practiced at lowered pressures and temperatures; however, pressures of in the order of 200-400 atmospheres are preferred, but higher or lower pressures may be used. Temperature of in excess of 300 C. are preferred, however, lower temperatures may be used; the upper limit of usable temperatures being that temperature that causes no inordinate coking action.

Some of the starting materials in which toxicity may be induced in accordance with the present invention may contain high molecular complexes that are especially susceptible to thermal degradation; these materials may have toxicity induced therein while higher pressures obtain with the added benefit that such mok-:cular complexes are reduced to greater extent, thereby enhancing toxicity induction.

The time element of the present invention in the second cycle of hydrogen action is not circumscribed by any definite time limit, but is induction; using some starting feed periods of 30 minutes or less will result in enhanced toxicity; periods of one hour or lon-ger may be used.

The first cycle of hydrogen action that reduces sulphur content may be accomplished in the presence of a catalyst. Catalysts effective in the presence of hydrogen are usable, as for instance the oxides and/ or suldes of molybdenum, vanadium, uranium, cobalt, tin, manganese, tungsten, or the like.

In the disclosures herein made the removing of loW boiling fractions by gas movement or pressure release is considered `the equivalent of distillation.

When reference is made to high molecular complexes contained in the starting material, and When the starting material contains low boiling fractions that are not considered high molecular complexes, it is of course obvious that the high molecular complexes contained in the starting material are to a certain extent depolymerized by the solvent present.

Starting materials of the present process also include tars of aromatic content from which low boiling fractions have been removed, as for instance tars from which solvent oils have been removed. Viewed broadly, the starting materials of the present process are sulphur bearing tars of aromatic content, fractions of said tar more viscous than the starting material due to removal of low boiling fractions from the starting material, high boiling fractions and pitches derived therefrom.

The term pitch as used herein includes the higher boiling fractions of tar, in other Words, Y

tar from Which low boiling ends have been stripped, such loW boiling ends being suitable for use per se as creosote, other wood preservative, or solvent. For instance, the final residue resulting from evaporating tar to dryness and then stripping wood preservative from the distillate is a very suitable pitch for use as a starting material of the present process.

It will be seen that by reduction of sulfur content of the material under treatment during any stage of hydrogen action, the oxide catalyst used during subsequent stages is at least partially protected from the effect of the sulfur.

Minor changes may be made Without departing from the spirit of the invention.

Iclaim:

1. In the production of an oil of the Wood preserving type the process which comprises: subjecting a sulfur-bearing mixture of high temperature of coal tar fractions to the sulfur reducing action of hydrogen; thereafter subjecting said sulfur rened material to further hydrogen action at a pressure in excess of atmospheric and a temperature in excess of 300 C. in the presence of an oxide catalyst and an additional catalytic material selected from the group consisting of halogens, halids and derivatives thereof including substitution and addition products thereof, whereby to reduce coke residue, specific gravity and viscosity; carrying on the process for such a length of time as to provide an oil of the Wood preserving type having induced toxicity and conforming in boiling range to specifications accepted in the trade for a tar-derived Wood preserving impregnant, and being further characterized by a substantial residue above 325 C.

2. In the production of an oil of the wood preserving type, the process which comprises: subjecting a sulfur-bearing mixture of high temperature coal tar fractions to the sulfur reducing action of hydrogen at a temperature not substantially less than 350 C.; thereafter subjecting said sulfur refined material to the action of a flow of hydrogen not substantially less than 8,000 cubic feet per barrel material at a temperature and pressure not substantially less than 300 C. and 200 atmospheres, respectively, while contacting an oxide catalyst and an additional catalytic material selected from the group consisting of halogens, halids and derivatives thereof including substitution and addition products thereof, whereby to reduce coke residue, specific gravity and viscosity; carrying on the process for such a length of time as to provide an oil of the Wood preserving type having induced toxicity and conforming in boiling range to specifications accepted in the trade for a tar-derived Wood preserving impregnant, and being further characterized by a substantial residue above 325 C.

JACQUELIN E. HARVEY, JR. 

